The invention relates to the field of signal biasing and scaling circuits and more particularly scaling and biasing circuits for use with small signal transducers.
Since transducers, such as accelerometers, used in telemetry systems generally have small signal outputs that are of both a positive and negative polarity, it is quite often necessary to convert those outputs to signals of a single polarity due to the fact that many of the telemetry systems require that the input signals be of a single polarity and of a limited voltage range such as 0 to 5 volts DC. Also due to the fact that telemetry systems often require signals of great accuracy, it is highly desirable that any biasing or scaling circuits introduce an absolute minimum of error into the signals. In addition, many of the prior art biasing and scaling circuits used with telemetry systems require a negative source of DC voltage which in many cases is not available within the telemetry system itself.
In other prior art systems utilizing positive voltage sources in combination with transistor elements, quite often errors are introduced into the signal output due to temperature effects on the transistors or result from the base currents in the transistors themselves. In addition the current voltage characteristics of the transistor elements tended to vary with temperature thereby adding an additional source of error.